DOI:10.1049/ree.1969.0085

出版商:IERE    

年代:1969

数据来源: IET

摘要:

The automatic picture transmission (APT) sub-system carried on weather satellites transmits, at facsimile rate, cloud cover photographs of the Earth below. Frequency modulation of a carrier in the 137 MHz band transmitted at a level of 5 watts is used to give pictures representing an area approximately 2400 km (1500 miles) square with an average resolution of 3 km (2 miles).Major factors governing the design of a ground station which has been operational since early 1967 are presented. Signal/noise considerations show that a desirable combination is a tracking antenna having a gain of 10 dB followed by a receiving system having a noise figure not greater than 4 dB. Except for a doubling of line frequency a standard wire facsimile is used for final picture print-out.Many additions to, and refinements of, the basic station are possible. A few of these are outlined and assessed in terms of operational convenience.

DOI:10.1049/ree.1969.0086

出版商:IERE    

年代:1969

数据来源: IET

摘要:

Karnaugh Map methods for designing counters and shift registers can be extended to parallel code conversion or interface design. A number of examples are shown, including the derivation of some wellknown circuits. The possibility of steering J-K and D type flip-flops is considered. Finally, an example illustrating the use of a three-dimensional Karnaugh Map is given.

DOI:10.1049/ree.1969.0087

出版商:IERE    

年代:1969

数据来源: IET

摘要:

A transistor circuit for silicon integrated circuit construction incorporating a new design of modulator is described. The circuit is associated with a microphone amplifier and r.f. input stage. The output consists of an amplitude modulated carrier in which the a.f. components have been suppressed. The circuit is suitable for modulation frequencies well into the video range and carrier frequencies up to about 20 MHz, the behaviour being predictable over a wide range of conditions. The specifications meet those laid down for integrated circuits generally.

DOI:10.1049/ree.1969.0088

出版商:IERE    

年代:1969

数据来源: IET

摘要:

Analysis of diode modulators and mixers is complicated by the need to examine the ratio of source to load impedance. In a number of circuits the optimum ratio is unity, and it is pointed out that a set of conditions can be developed, allowing this to be predicted in most cases before analysis.

DOI:10.1049/ree.1969.0089

出版商:IERE    

年代:1969

数据来源: IET

摘要:

An instrument which integrates the number of minutes during which average light intensity falls between or outside nine pre-set levels is described. The primary use of the equipment is in the study of the response of plants to light. The technique may have other applications.

DOI:10.1049/ree.1969.0090

出版商:IERE    

年代:1969

数据来源: IET

摘要:

Typical load cell characteristics are listed and some factors concerning loading are given. An all-electronic system for digitizing the output of load cells directly is described, and details are given of some basic systems used to obtain control and information facilities from the digital weight-signals, with some fundamentals of the binary arithmetic used. Some weighing applications are mentioned and a computer-controlled weighing system is briefly described.

DOI:10.1049/ree.1969.0091

出版商:IERE    

年代:1969

数据来源: IET

摘要:

This paper describes the latitude, altitude, azimuth and polarization angle dependence of scattering of radio waves in the ionosphere. The anisotropic behaviour which arises due to the presence of the geomagnetic field has been taken into account. The formula obtained for scattering cross-section may be verified experimentally and the importance of the geomagnetic field in the production of anisotropy may then be analysed.

DOI:10.1049/ree.1969.0092

出版商:IERE    

年代:1969

数据来源: IET

摘要:

The paper considers the factors that influence the servo design for satellite tracking antennae. The methods of servo compensation are discussed and simple adaptive techniques are illustrated. The importance of the mechanics in relation to the servo performance is emphasized and the application of digital computers in servo tracking loops is discussed. A ‘design’ example is given.

DOI:10.1049/ree.1969.0093

出版商:IERE    

年代:1969

数据来源: IET

摘要:

The circuit described has good stability and long delay periods with good load-driving capabilities. A modified circuit is also presented which has stable delay periods even when large transient voltages are present on the supply, such as can be experienced in an industrial environment.

DOI:10.1049/ree.1969.0094

出版商:IERE    

年代:1969

数据来源: IET